Primary signet-ring cell/histiocytoid carcinoma of the eyelid: a clinicopathologic study of 5 cases and review of the literature.

Primary cutaneous signet-ring cell carcinomas are rare and aggressive neoplasms. These neoplasms have been mostly described in the eyelids, and more uncommonly, in the axillary skin. Histopathologically, the neoplasm seems to be composed of signet-ring cells or histiocytoid epithelial cells arranged in an Indian file growth pattern between collagen bundles of the dermis. Immunohistochemically, neoplastic cells expressed strong diffuse reactivity for CAM 5.2, CK7, high molecular weight CK, AE1/AE3 and MNF116 cytokeratins, carcinoembryonic antigen, epithelial membrane antigen, gross cystic disease fluid protein-15, p63, mucin-1 (MUC-1), BerEP4, and E-cadherin; moderate positivity for α-smooth muscle actin, tissue-specific transcription factor 1, MUC-2, Podoplanin, and N-cadherin; and weak positivity for epidermal growth factor receptor. Estrogen and progesterone receptors show positive results in some cases and negative results in others. The histopathologic and immunohistochemical features of primary signet-ring cell or histiocytoid carcinoma of the eyelid are closely similar to those of histiocytoid lobular carcinoma of the breast, and there are several examples of histiocytoid mammary carcinoma metastatic to the eyelids. Therefore, histopathologic differential diagnosis between primary and metastatic signet-ring cell or histiocytoid eyelid carcinomas is mandatory. In this study, we report our experience with the clinical, histopathologic, and immunohistochemical findings in 5 cases of primary signet-ring cell or histiocytoid carcinoma of the eyelid. We investigated the usefulness of p63, epidermal growth factor receptor, MUC-1, MUC-2, mammaglobin, and E-cadherin as immunohistochemical markers for this histopathologic differential diagnosis. Primary signet-ring cell carcinoma of the eyelid is an aggressive neoplasm that may develop regional or distant metastases, and therefore, it should be excised with wide margins.

The hypointense liver lesion on T2-weighted MR images and what it means.

The vast majority of focal liver lesions are hyperintense on T2-weighted magnetic resonance (MR) images. Rarely, however, hepatic nodules may appear totally or partially hypointense on those images. Causes for this uncommon appearance include deposition of iron, calcium, or copper and are related to the presence of blood degradation products, macromolecules, coagulative necrosis, and other conditions. Although rare, low signal intensity relative to surrounding liver on T2-weighted images may be seen in a wide spectrum of lesions. Examples include cases of focal nodular hyperplasia, hepatocellular adenoma, hepatocellular carcinoma, metastases, leiomyoma, siderotic or dysplastic nodules, nodules in Wilson disease, granuloma, and hydatid cyst. On fat-suppressed T2-weighted images, nodules with a lipomatous component, such as lipoma, angiomyolipoma, hepatocellular adenoma, and hepatocellular carcinoma may also appear partially or totally hypointense. The conjunction of other MR imaging findings and their integration in the clinical setting may allow a correct diagnosis in a considerable proportion of cases. The cause for T2-weighted hypointensity may not be, however, always recognized, and only pathologic correlation may provide the answer. The aims of this work are to discuss the causes and mechanisms of hypointensity of liver lesions on T2-weighted images and proposing an algorithm for classification that may be useful as a quick reminder for the interested reader.